MONDAY, July 6 (HealthDay News) -- The human papillomavirus (HPV) vaccine is highly effective at preventing precancerous cervical lesions that can lead to cervical cancer, a new study shows.

The researchers also found that the HPV-16/18 AS04-adjuvanted vaccine also appears to protect against other cancer-causing HPV types closely related to HPV-16/18, most notably HPV-31 and HPV-45.

The study of women aged 15 to 25, who received three vaccine doses over six months, found that it was as much as 98 percent effective against HPV-16/18, and between 37 percent and 54 percent effective against 12 other cancer-causing HPV types.

HPV-16/18 causes about 70 percent of cervical cancer cases, while the remaining 30 percent of cases are caused by other cancer-causing HPV types. The cross-protective effect of the HPV-16/18 vaccine could provide an additional 11 percent to 16 percent protection against cervical cancer.

"Although the importance of continued tests for Pap or HPV in vaccinated and unvaccinated women must be emphasized, HPV vaccination has the potential to substantially reduce the incidence of cervical cancer and precancer, and the numbers of colposcopy referrals and cervical excision procedures," concluded Dr. Jorma Paavonen, of the University of Helsinki in Finland, and colleagues.

The study, which was funded by GlaxoSmithKline Biologicals, maker of the HPV-16/18 AS04-adjuvanted vaccine Cervarix, appears online July 7 and in an upcoming print issue of The Lancet.

In an accompanying editorial, two experts wrote that men must also be included in efforts to halt the spread of HPV.

"Currently, the targets for HPV vaccination are girls and young women aged 11 to 26 years prior to sexual debut," noted Karin B. Michels, of Harvard Medical School in Boston, and Dr. Harald zur Hausen, of the German Cancer Research Center in Heidelberg.

"While good utilization of the [vaccine] program will reduce cervical cancer incidence in a couple of decades, this subgroup of the population at risk is too small to limit the spread of the virus," the researchers wrote. "The only efficient way to stop the virus is to also vaccinate the other half of the sexually active population: boys and men."